What Divers Should Know About Scalloped Hammerhead Sharks

The scalloped hammerhead shark (Sphyrna lewini) is a globally distributed species, instantly recognizable by its uniquely shaped head. This distinct cephalofoil features a central indentation along the anterior margin, flanked by two more on either side, giving it the characteristic "scalloped" appearance. These are fairly large hammerheads; males typically measure 1.5 to 1.8 meters (5 to 6 feet) at maturity, while females often reach 2.5 meters (8 feet), with the largest individuals documented up to 4.3 meters (14 feet) in length. They inhabit warm temperate and tropical coastal waters worldwide.

Divers typically encounter scalloped hammerheads over continental and insular shelves, often in depths above 25 meters (82 feet), though their full range extends to over 500 meters (1,600 feet). During daylight hours, these sharks are frequently found closer to shore. A truly remarkable aspect of their behavior is their schooling; adults can aggregate in large groups numbering in the hundreds, creating a dynamic spectacle that can be observed during the day, night, or morning depending on location and their movements.